15. 3Sum

```Solution.c /** * Return an array of arrays of size *returnSize. * The sizes of the arrays are returned as *returnColumnSizes array. * Note: Both returned array and *columnSizes array must be malloced, assume caller calls free(). */ int cmp(const void* a, const void* b) { return *(int*)a - *(int*)b; } int** threeSum(int* nums, int numsSize, int* returnSize, int** returnColumnSizes) { qsort(nums, numsSize, sizeof(int), cmp); int capacity = 1000, count = 0; int** res = malloc(capacity * sizeof(int*)); *returnColumnSizes = malloc(capacity * sizeof(int)); for (int i = 0; i < numsSize - 2; ++i) { if (i > 0 && nums[i] == nums[i - 1]) continue; int l = i + 1, r = numsSize - 1; while (l < r) { int sum = nums[i] + nums[l] + nums[r]; if (sum < 0) l++; else if (sum > 0) r--; else { if (count == capacity) { capacity *= 2; res = realloc(res, capacity * sizeof(int*)); *returnColumnSizes = realloc(*returnColumnSizes, capacity * sizeof(int)); } res[count] = malloc(3 * sizeof(int)); res[count][0] = nums[i]; res[count][1] = nums[l]; res[count][2] = nums[r]; (*returnColumnSizes)[count++] = 3; while (l < r && nums[l] == nums[l + 1]) l++; while (l < r && nums[r] == nums[r - 1]) r--; l++; r--; } } } *returnSize = count; return res; } ``` ```Solution.cpp class Solution { public: vector<vector<int>> threeSum(vector<int>& nums) { vector<vector<int>> res; sort(nums.begin(), nums.end()); int n = nums.size(); for (int i = 0; i < n - 2; ++i) { if (i > 0 && nums[i] == nums[i - 1]) continue; int l = i + 1, r = n - 1; while (l < r) { int s = nums[i] + nums[l] + nums[r]; if (s < 0) ++l; else if (s > 0) --r; else { res.push_back({nums[i], nums[l], nums[r]}); while (l < r && nums[l] == nums[l + 1]) ++l; while (l < r && nums[r] == nums[r - 1]) --r; ++l; --r; } } } return res; } }; ``` ```Solution.cs public class Solution { public IList<IList<int>> ThreeSum(int[] nums) { Array.Sort(nums); var res = new List<IList<int>>(); for (int i = 0; i < nums.Length - 2; i++) { if (i > 0 && nums[i] == nums[i - 1]) continue; int l = i + 1, r = nums.Length - 1; while (l < r) { int sum = nums[i] + nums[l] + nums[r]; if (sum < 0) l++; else if (sum > 0) r--; else { res.Add(new List<int> { nums[i], nums[l], nums[r] }); while (l < r && nums[l] == nums[l + 1]) l++; while (l < r && nums[r] == nums[r - 1]) r--; l++; r--; } } } return res; } } ``` ```Solution.dart class Solution { List<List<int>> threeSum(List<int> nums) { nums.sort(); List<List<int>> res = []; for (int i = 0; i < nums.length - 2; i++) { if (i > 0 && nums[i] == nums[i - 1]) continue; int l = i + 1, r = nums.length - 1; while (l < r) { int sum = nums[i] + nums[l] + nums[r]; if (sum < 0) { l++; } else if (sum > 0) { r--; } else { res.add([nums[i], nums[l], nums[r]]); while (l < r && nums[l] == nums[l + 1]) l++; while (l < r && nums[r] == nums[r - 1]) r--; l++; r--; } } } return res; } } ``` ```Solution.erl -spec three_sum([integer()]) -> [[integer()]]. three_sum(Nums) -> Sorted = lists:sort(Nums), Tuple = list_to_tuple(Sorted), Len = tuple_size(Tuple), three_sum_loop(Tuple, 1, Len, []). three_sum_loop(_T, I, Len, Acc) when I > Len - 2 -> lists:reverse(Acc); three_sum_loop(T, I, Len, Acc) -> A = element(I, T), case (I > 1) andalso (A =:= element(I - 1, T)) of true -> three_sum_loop(T, I + 1, Len, Acc); false -> Acc1 = two_sum(T, I, I + 1, Len, A, Acc), three_sum_loop(T, I + 1, Len, Acc1) end. two_sum(_T, _I, Left, Right, _A, Acc) when Left >= Right -> Acc; two_sum(T, I, Left, Right, A, Acc) -> B = element(Left, T), C = element(Right, T), Sum = A + B + C, case Sum of 0 -> Triplet = [A, B, C], NewAcc = [Triplet | Acc], NewLeft = skip_forward(T, B, Left + 1, Right), NewRight = skip_backward(T, C, NewLeft, Right - 1), two_sum(T, I, NewLeft, NewRight, A, NewAcc); _ when Sum < 0 -> two_sum(T, I, Left + 1, Right, A, Acc); _ -> two_sum(T, I, Left, Right - 1, A, Acc) end. skip_forward(T, Val, Pos, Right) when Pos =< Right, element(Pos, T) =:= Val -> skip_forward(T, Val, Pos + 1, Right); skip_forward(_T, _Val, Pos, _Right) -> Pos. skip_backward(T, Val, Left, Pos) when Pos >= Left, element(Pos, T) =:= Val -> skip_backward(T, Val, Left, Pos - 1); skip_backward(_T, _Val, _Left, Pos) -> Pos. ``` ```Solution.ex defmodule Solution do @SPEC three_sum(nums :: [integer]) :: [[integer]] def three_sum(nums) do nums = List.to_tuple(Enum.sort(nums)) do_three_sum(nums, 0, tuple_size(nums), []) end defp do_three_sum(nums, i, len, acc) do val_i = elem(nums, i) cond do val_i > 0 or i > len - 3 -> acc i == 0 or elem(nums, i - 1) != val_i -> acc = find_triplets(nums, i, i + 1, len - 1, acc) do_three_sum(nums, i + 1, len, acc) true -> do_three_sum(nums, i + 1, len, acc) end end defp find_triplets(_nums, _i, l, r, acc) when l >= r, do: acc defp find_triplets(nums, i, l, r, acc) do val_i = elem(nums, i) val_l = elem(nums, l) val_r = elem(nums, r) sum = val_i + val_l + val_r cond do sum > 0 -> find_triplets(nums, i, l, r - 1, acc) sum < 0 -> find_triplets(nums, i, l + 1, r, acc) true -> acc = [[val_i, val_l, val_r] | acc] l = grow_from_left(nums, l + 1, r, val_l) r = shrink_from_right(nums, l, r - 1, val_r) find_triplets(nums, i, l, r, acc) end end defp shrink_from_right(nums, l, r, prev_val_r) do cond do r <= l or elem(nums, r) != prev_val_r -> r true -> shrink_from_right(nums, l, r - 1, prev_val_r) end end defp grow_from_left(nums, l, r, prev_val_l) do cond do l >= r or elem(nums, l) != prev_val_l -> l true -> grow_from_left(nums, l + 1, r, prev_val_l) end end end ``` ```Solution.go func threeSum(nums []int) [][]int { sort.Ints(nums) res := [][]int{} for i := 0; i < len(nums)-2; i++ { if i > 0 && nums[i] == nums[i-1] { continue } l, r := i+1, len(nums)-1 for l < r { sum := nums[i] + nums[l] + nums[r] if sum < 0 { l++ } else if sum > 0 { r-- } else { res = append(res, []int{nums[i], nums[l], nums[r]}) for l < r && nums[l] == nums[l+1] { l++ } for l < r && nums[r] == nums[r-1] { r-- } l++ r-- } } } return res } ``` ```Solution.java class Solution { public List<List<Integer>> threeSum(int[] nums) { List<List<Integer>> res = new ArrayList<>(); Arrays.sort(nums); for (int i = 0; i < nums.length - 2; ++i) { if (i > 0 && nums[i] == nums[i - 1]) continue; int l = i + 1, r = nums.length - 1; while (l < r) { int sum = nums[i] + nums[l] + nums[r]; if (sum < 0) l++; else if (sum > 0) r--; else { res.add(Arrays.asList(nums[i], nums[l], nums[r])); while (l < r && nums[l] == nums[l + 1]) l++; while (l < r && nums[r] == nums[r - 1]) r--; l++; r--; } } } return res; } } ``` ```Solution.js /** * @param {number[]} nums * @return {number[][]} */ var threeSum = function(nums) { nums.sort((a, b) => a - b); const res = []; for (let i = 0; i < nums.length - 2; i++) { if (i > 0 && nums[i] === nums[i - 1]) continue; let l = i + 1, r = nums.length - 1; while (l < r) { const sum = nums[i] + nums[l] + nums[r]; if (sum < 0) l++; else if (sum > 0) r--; else { res.push([nums[i], nums[l], nums[r]]); while (l < r && nums[l] === nums[l + 1]) l++; while (l < r && nums[r] === nums[r - 1]) r--; l++; r--; } } } return res; }; ``` ```Solution.kt class Solution { fun threeSum(nums: IntArray): List<List<Int>> { nums.sort() val res = mutableListOf<List<Int>>() for (i in 0 until nums.size - 2) { if (i > 0 && nums[i] == nums[i - 1]) continue var l = i + 1 var r = nums.size - 1 while (l < r) { val sum = nums[i] + nums[l] + nums[r] when { sum < 0 -> l++ sum > 0 -> r-- else -> { res.add(listOf(nums[i], nums[l], nums[r])) while (l < r && nums[l] == nums[l + 1]) l++ while (l < r && nums[r] == nums[r - 1]) r-- l++ r-- } } } } return res } } ``` ```Solution.php class Solution { /** * @param Integer[] $nums * @return Integer[][] */ function threeSum($nums) { sort($nums); $res = []; $n = count($nums); for ($i = 0; $i < $n - 2; $i++) { if ($i > 0 && $nums[$i] == $nums[$i - 1]) continue; $l = $i + 1; $r = $n - 1; while ($l < $r) { $sum = $nums[$i] + $nums[$l] + $nums[$r]; if ($sum < 0) $l++; else if ($sum > 0) $r--; else { $res[] = [$nums[$i], $nums[$l], $nums[$r]]; while ($l < $r && $nums[$l] == $nums[$l + 1]) $l++; while ($l < $r && $nums[$r] == $nums[$r - 1]) $r--; $l++; $r--; } } } return $res; } } ``` ```Solution.py class Solution: def threeSum(self, nums): res = [] nums.sort() for i in range(len(nums) - 2): if i > 0 and nums[i] == nums[i - 1]: continue l, r = i + 1, len(nums) - 1 while l < r: total = nums[i] + nums[l] + nums[r] if total < 0: l += 1 elif total > 0: r -= 1 else: res.append([nums[i], nums[l], nums[r]]) while l < r and nums[l] == nums[l + 1]: l += 1 while l < r and nums[r] == nums[r - 1]: r -= 1 l += 1; r -= 1 return res ``` ```Solution.rb def three_sum(nums) nums.sort! res = [] (0...nums.length - 2).each do |i| next if i > 0 && nums[i] == nums[i - 1] l, r = i + 1, nums.length - 1 while l < r sum = nums[i] + nums[l] + nums[r] if sum < 0 l += 1 elsif sum > 0 r -= 1 else res << [nums[i], nums[l], nums[r]] l += 1 r -= 1 l += 1 while l < r && nums[l] == nums[l - 1] r -= 1 while l < r && nums[r] == nums[r + 1] end end end res end ``` ```Solution.rkt (define/contract (three-sum nums) (-> (listof exact-integer?) (listof (listof exact-integer?))) (define sorted (sort nums <)) (define sorted-vec (list->vector sorted)) (define len (vector-length sorted-vec)) (define (loop i acc) (if (>= i (- len 2)) (reverse acc) (if (and (> i 0) (= (vector-ref sorted-vec i) (vector-ref sorted-vec (- i 1)))) (loop (+ i 1) acc) (let two-pointer ([l (+ i 1)] [r (- len 1)] [acc acc]) (if (>= l r) (loop (+ i 1) acc) (let* ([a (vector-ref sorted-vec i)] [b (vector-ref sorted-vec l)] [c (vector-ref sorted-vec r)] [sum (+ a b c)]) (cond [(< sum 0) (two-pointer (+ l 1) r acc)] [(> sum 0) (two-pointer l (- r 1) acc)] [else (define new-acc (cons (list a b c) acc)) (define (skip-left l) (let loop-l ([l l]) (if (and (< (+ l 1) r) (= (vector-ref sorted-vec l) (vector-ref sorted-vec (+ l 1)))) (loop-l (+ l 1)) (+ l 1)))) (define (skip-right r) (let loop-r ([r r]) (if (and (> (- r 1) l) (= (vector-ref sorted-vec r) (vector-ref sorted-vec (- r 1)))) (loop-r (- r 1)) (- r 1)))) (two-pointer (skip-left l) (skip-right r) new-acc)]))))))) (loop 0 '())) ``` ```Solution.rs impl Solution { pub fn three_sum(mut nums: Vec<i32>) -> Vec<Vec<i32>> { nums.sort(); let mut res = vec![]; for i in 0..nums.len() { if i > 0 && nums[i] == nums[i - 1] { continue; } let (mut l, mut r) = (i + 1, nums.len() - 1); while l < r { let sum = nums[i] + nums[l] + nums[r]; if sum < 0 { l += 1; } else if sum > 0 { r -= 1; } else { res.push(vec![nums[i], nums[l], nums[r]]); while l < r && nums[l] == nums[l + 1] { l += 1; } while l < r && nums[r] == nums[r - 1] { r -= 1; } l += 1; r -= 1; } } } res } } ``` ```Solution.scala object Solution { def threeSum(nums: Array[Int]): List[List[Int]] = { val sorted = nums.sorted var res = List[List[Int]]() for (i <- 0 until sorted.length - 2) { if (i == 0 || sorted(i) != sorted(i - 1)) { var l = i + 1 var r = sorted.length - 1 while (l < r) { val sum = sorted(i) + sorted(l) + sorted(r) if (sum < 0) l += 1 else if (sum > 0) r -= 1 else { res ::= List(sorted(i), sorted(l), sorted(r)) while (l < r && sorted(l) == sorted(l + 1)) l += 1 while (l < r && sorted(r) == sorted(r - 1)) r -= 1 l += 1 r -= 1 } } } } res } } ``` ```Solution.swift class Solution { func threeSum(_ nums: [Int]) -> [[Int]] { let nums = nums.sorted() var res = [[Int]]() for i in 0..<nums.count - 2 { if i > 0 && nums[i] == nums[i - 1] { continue } var l = i + 1, r = nums.count - 1 while l < r { let sum = nums[i] + nums[l] + nums[r] if sum < 0 { l += 1 } else if sum > 0 { r -= 1 } else { res.append([nums[i], nums[l], nums[r]]) while l < r && nums[l] == nums[l + 1] { l += 1 } while l < r && nums[r] == nums[r - 1] { r -= 1 } l += 1 r -= 1 } } } return res } } ``` ```Solution.ts function threeSum(nums: number[]): number[][] { nums.sort((a, b) => a - b); const res: number[][] = []; for (let i = 0; i < nums.length - 2; i++) { if (i > 0 && nums[i] === nums[i - 1]) continue; let l = i + 1, r = nums.length - 1; while (l < r) { const sum = nums[i] + nums[l] + nums[r]; if (sum < 0) l++; else if (sum > 0) r--; else { res.push([nums[i], nums[l], nums[r]]); while (l < r && nums[l] === nums[l + 1]) l++; while (l < r && nums[r] === nums[r - 1]) r--; l++; r--; } } } return res; } ```

Author: nendroids

sol/solution/0001-0100/0015/README.md

@@ -0,0 +1,35 @@
+# [**15. 3Sum**](https://leetcode.com/problems/3sum/description/)
+
+Given an integer array nums, return all the triplets `[nums[i]`, `nums[j]`, `nums[k]]` such that `i != j`, `i != k`, and `j != k`, and `nums[i] + nums[j] + nums[k] == 0`.
+
+Notice that the solution set must not contain duplicate triplets
+
+#### **Example 1:**
+```md
+Input: nums = [-1,0,1,2,-1,-4]
+Output: [[-1,-1,2],[-1,0,1]]
+Explanation: 
+nums[0] + nums[1] + nums[2] = (-1) + 0 + 1 = 0.
+nums[1] + nums[2] + nums[4] = 0 + 1 + (-1) = 0.
+nums[0] + nums[3] + nums[4] = (-1) + 2 + (-1) = 0.
+The distinct triplets are [-1,0,1] and [-1,-1,2].
+Notice that the order of the output and the order of the triplets does not matter.
+```
+
+#### **Example 2:**
+```md
+Input: nums = [0,1,1]
+Output: []
+Explanation: The only possible triplet does not sum up to 0.
+```
+
+#### **Example 3:**
+```md
+Input: nums = [0,0,0]
+Output: [[0,0,0]]
+Explanation: The only possible triplet sums up to 0.
+```
+
+#### **Constraints:**
+> - `3 <= nums.length <= 3000`
+> - `-10⁵ <= nums[i] <= 10⁵` 

sol/solution/0001-0100/0015/Solution.c

@@ -0,0 +1,36 @@
+/**
+ * Return an array of arrays of size *returnSize.
+ * The sizes of the arrays are returned as *returnColumnSizes array.
+ * Note: Both returned array and *columnSizes array must be malloced, assume caller calls free().
+ */
+int cmp(const void* a, const void* b) { return *(int*)a - *(int*)b; }
+int** threeSum(int* nums, int numsSize, int* returnSize, int** returnColumnSizes) {
+ qsort(nums, numsSize, sizeof(int), cmp);
+ int capacity = 1000, count = 0;
+ int** res = malloc(capacity * sizeof(int*));
+ *returnColumnSizes = malloc(capacity * sizeof(int));
+ for (int i = 0; i < numsSize - 2; ++i) {
+ if (i > 0 && nums[i] == nums[i - 1]) continue;
+ int l = i + 1, r = numsSize - 1;
+ while (l < r) {
+ int sum = nums[i] + nums[l] + nums[r];
+ if (sum < 0) l++;
+ else if (sum > 0) r--;
+ else {
+ if (count == capacity) {
+ capacity *= 2;
+ res = realloc(res, capacity * sizeof(int*));
+ *returnColumnSizes = realloc(*returnColumnSizes, capacity * sizeof(int));
+ }
+ res[count] = malloc(3 * sizeof(int));
+ res[count][0] = nums[i]; res[count][1] = nums[l]; res[count][2] = nums[r];
+ (*returnColumnSizes)[count++] = 3;
+ while (l < r && nums[l] == nums[l + 1]) l++;
+ while (l < r && nums[r] == nums[r - 1]) r--;
+ l++; r--;
+ }
+ }
+ }
+ *returnSize = count;
+ return res;
+}

sol/solution/0001-0100/0015/Solution.cpp

@@ -0,0 +1,24 @@
+class Solution {
+public:
+ vector<vector<int>> threeSum(vector<int>& nums) {
+ vector<vector<int>> res;
+ sort(nums.begin(), nums.end());
+ int n = nums.size();
+ for (int i = 0; i < n - 2; ++i) {
+ if (i > 0 && nums[i] == nums[i - 1]) continue;
+ int l = i + 1, r = n - 1;
+ while (l < r) {
+ int s = nums[i] + nums[l] + nums[r];
+ if (s < 0) ++l;
+ else if (s > 0) --r;
+ else {
+ res.push_back({nums[i], nums[l], nums[r]});
+ while (l < r && nums[l] == nums[l + 1]) ++l;
+ while (l < r && nums[r] == nums[r - 1]) --r;
+ ++l; --r;
+ }
+ }
+ }
+ return res;
+ }
+};

sol/solution/0001-0100/0015/Solution.cs

@@ -0,0 +1,22 @@
+public class Solution {
+ public IList<IList<int>> ThreeSum(int[] nums) {
+ Array.Sort(nums);
+ var res = new List<IList<int>>();
+ for (int i = 0; i < nums.Length - 2; i++) {
+ if (i > 0 && nums[i] == nums[i - 1]) continue;
+ int l = i + 1, r = nums.Length - 1;
+ while (l < r) {
+ int sum = nums[i] + nums[l] + nums[r];
+ if (sum < 0) l++;
+ else if (sum > 0) r--;
+ else {
+ res.Add(new List<int> { nums[i], nums[l], nums[r] });
+ while (l < r && nums[l] == nums[l + 1]) l++;
+ while (l < r && nums[r] == nums[r - 1]) r--;
+ l++; r--;
+ }
+ }
+ }
+ return res;
+ }
+}

sol/solution/0001-0100/0015/Solution.dart

@@ -0,0 +1,25 @@
+class Solution {
+ List<List<int>> threeSum(List<int> nums) {
+ nums.sort();
+ List<List<int>> res = [];
+ for (int i = 0; i < nums.length - 2; i++) {
+ if (i > 0 && nums[i] == nums[i - 1]) continue;
+ int l = i + 1, r = nums.length - 1;
+ while (l < r) {
+ int sum = nums[i] + nums[l] + nums[r];
+ if (sum < 0) {
+ l++;
+ } else if (sum > 0) {
+ r--;
+ } else {
+ res.add([nums[i], nums[l], nums[r]]);
+ while (l < r && nums[l] == nums[l + 1]) l++;
+ while (l < r && nums[r] == nums[r - 1]) r--;
+ l++;
+ r--;
+ }
+ }
+ }
+ return res;
+ }
+}

sol/solution/0001-0100/0015/Solution.erl

@@ -0,0 +1,43 @@
+-spec three_sum([integer()]) -> [[integer()]].
+three_sum(Nums) ->
+ Sorted = lists:sort(Nums),
+ Tuple = list_to_tuple(Sorted),
+ Len = tuple_size(Tuple),
+ three_sum_loop(Tuple, 1, Len, []).
+three_sum_loop(_T, I, Len, Acc) when I > Len - 2 ->
+ lists:reverse(Acc);
+three_sum_loop(T, I, Len, Acc) ->
+ A = element(I, T),
+ case (I > 1) andalso (A =:= element(I - 1, T)) of
+ true ->
+ three_sum_loop(T, I + 1, Len, Acc);
+ false ->
+ Acc1 = two_sum(T, I, I + 1, Len, A, Acc),
+ three_sum_loop(T, I + 1, Len, Acc1)
+ end.
+two_sum(_T, _I, Left, Right, _A, Acc) when Left >= Right ->
+ Acc;
+two_sum(T, I, Left, Right, A, Acc) ->
+ B = element(Left, T),
+ C = element(Right, T),
+ Sum = A + B + C,
+ case Sum of
+ 0 ->
+ Triplet = [A, B, C],
+ NewAcc = [Triplet | Acc],
+ NewLeft = skip_forward(T, B, Left + 1, Right),
+ NewRight = skip_backward(T, C, NewLeft, Right - 1),
+ two_sum(T, I, NewLeft, NewRight, A, NewAcc);
+ _ when Sum < 0 ->
+ two_sum(T, I, Left + 1, Right, A, Acc);
+ _ ->
+ two_sum(T, I, Left, Right - 1, A, Acc)
+ end.
+skip_forward(T, Val, Pos, Right) when Pos =< Right, element(Pos, T) =:= Val ->
+ skip_forward(T, Val, Pos + 1, Right);
+skip_forward(_T, _Val, Pos, _Right) ->
+ Pos.
+skip_backward(T, Val, Left, Pos) when Pos >= Left, element(Pos, T) =:= Val ->
+ skip_backward(T, Val, Left, Pos - 1);
+skip_backward(_T, _Val, _Left, Pos) ->
+ Pos.

sol/solution/0001-0100/0015/Solution.ex

@@ -0,0 +1,49 @@
+defmodule Solution do
+ @spec three_sum(nums :: [integer]) :: [[integer]]
+ def three_sum(nums) do
+ nums = List.to_tuple(Enum.sort(nums))
+ do_three_sum(nums, 0, tuple_size(nums), [])
+ end
+ defp do_three_sum(nums, i, len, acc) do
+ val_i = elem(nums, i)
+ cond do
+ val_i > 0 or i > len - 3 ->
+ acc
+ i == 0 or elem(nums, i - 1) != val_i ->
+ acc = find_triplets(nums, i, i + 1, len - 1, acc)
+ do_three_sum(nums, i + 1, len, acc)
+ true ->
+ do_three_sum(nums, i + 1, len, acc)
+ end
+ end
+ defp find_triplets(_nums, _i, l, r, acc) when l >= r, do: acc
+ defp find_triplets(nums, i, l, r, acc) do
+ val_i = elem(nums, i)
+ val_l = elem(nums, l)
+ val_r = elem(nums, r)
+ sum = val_i + val_l + val_r
+ cond do
+ sum > 0 ->
+ find_triplets(nums, i, l, r - 1, acc)
+ sum < 0 ->
+ find_triplets(nums, i, l + 1, r, acc)
+ true ->
+ acc = [[val_i, val_l, val_r] | acc]
+ l = grow_from_left(nums, l + 1, r, val_l)
+ r = shrink_from_right(nums, l, r - 1, val_r)
+ find_triplets(nums, i, l, r, acc)
+ end
+ end
+ defp shrink_from_right(nums, l, r, prev_val_r) do
+ cond do
+ r <= l or elem(nums, r) != prev_val_r -> r
+ true -> shrink_from_right(nums, l, r - 1, prev_val_r)
+ end
+ end
+ defp grow_from_left(nums, l, r, prev_val_l) do
+ cond do
+ l >= r or elem(nums, l) != prev_val_l -> l
+ true -> grow_from_left(nums, l + 1, r, prev_val_l)
+ end
+ end
+end

sol/solution/0001-0100/0015/Solution.go

@@ -0,0 +1,29 @@
+func threeSum(nums []int) [][]int {
+ sort.Ints(nums)
+ res := [][]int{}
+ for i := 0; i < len(nums)-2; i++ {
+ if i > 0 && nums[i] == nums[i-1] {
+ continue
+ }
+ l, r := i+1, len(nums)-1
+ for l < r {
+ sum := nums[i] + nums[l] + nums[r]
+ if sum < 0 {
+ l++
+ } else if sum > 0 {
+ r--
+ } else {
+ res = append(res, []int{nums[i], nums[l], nums[r]})
+ for l < r && nums[l] == nums[l+1] {
+ l++
+ }
+ for l < r && nums[r] == nums[r-1] {
+ r--
+ }
+ l++
+ r--
+ }
+ }
+ }
+ return res
+}

sol/solution/0001-0100/0015/Solution.java

@@ -0,0 +1,22 @@
+class Solution {
+ public List<List<Integer>> threeSum(int[] nums) {
+ List<List<Integer>> res = new ArrayList<>();
+ Arrays.sort(nums);
+ for (int i = 0; i < nums.length - 2; ++i) {
+ if (i > 0 && nums[i] == nums[i - 1]) continue;
+ int l = i + 1, r = nums.length - 1;
+ while (l < r) {
+ int sum = nums[i] + nums[l] + nums[r];
+ if (sum < 0) l++;
+ else if (sum > 0) r--;
+ else {
+ res.add(Arrays.asList(nums[i], nums[l], nums[r]));
+ while (l < r && nums[l] == nums[l + 1]) l++;
+ while (l < r && nums[r] == nums[r - 1]) r--;
+ l++; r--;
+ }
+ }
+ }
+ return res;
+ }
+}

sol/solution/0001-0100/0015/Solution.js

@@ -0,0 +1,24 @@
+/**
+ * @param {number[]} nums
+ * @return {number[][]}
+ */
+var threeSum = function(nums) {
+ nums.sort((a, b) => a - b);
+ const res = [];
+ for (let i = 0; i < nums.length - 2; i++) {
+ if (i > 0 && nums[i] === nums[i - 1]) continue;
+ let l = i + 1, r = nums.length - 1;
+ while (l < r) {
+ const sum = nums[i] + nums[l] + nums[r];
+ if (sum < 0) l++;
+ else if (sum > 0) r--;
+ else {
+ res.push([nums[i], nums[l], nums[r]]);
+ while (l < r && nums[l] === nums[l + 1]) l++;
+ while (l < r && nums[r] === nums[r - 1]) r--;
+ l++; r--;
+ }
+ }
+ }
+ return res;
+};